| Case Name |
Explosion of accumulated substances on opening of exhaust piping at a semiconductor manufacturing factory |
| Pictograph |
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| Date |
August 14, 1996 |
| Place |
Uozu, Toyama, Japan |
| Location |
Semiconductor factory |
| Overview |
At a semiconductor manufacturing factory, periodic cleaning work for an exhaust pipe of a plasma CVD plant was carried out. During detaching operation of the blind flange, etc. with radio communication among remote workers, a fire and explosion occurred due to an operating procedure error caused by poor communication. The operation procedure seems to have been insufficient, considering hazardous operations in an exhaust system for semiconductors where many hazardous substances are used. There was a communication problem, and the communication technology that would prevent a mistake from happening should be considered. |
| Incident |
During periodic cleaning work of substances accumulated in exhaust piping of a plasma CVD plant, a worker removed a blind flange at the end of the piping, and an explosion occurred in the piping 1-5 minutes later. |
| Processing |
Consumption and usage |
| Process Flow |
Fig2.Unit process flow
|
| Substance |
Amorphous silicon hydride compound, Fig3 |
| Hydrogen, Fig4 |
| Type of Accident |
Explosion |
| Sequence |
Cleaning work was started by worker A, with B in the attic and worker C on the roof with communicating by radio. The cleaning work is as follows. Worker A detaches the blind flange of the exhaust piping, taking in the air from there, and powder that has piled up near the flange is transferred to a scrubber 44 m away. In order to isolate an evil elimination apparatus by bypassing, worker C intended to open the valve of the bypass line according to the operation standard and closed the block valves of the apparatus. Then there was a radio communication by worker A to ask worker C about detaching the blind flange. Worker C answered "Not yet". A back-pressure alarm sounded during valve switching work by C, and an explosion occurred just after starting to open the bypass valve. The correct procedure is; after bypassing the eliminating apparatus, the blind flange at the end is opened. Refer to Fig2. |
| Cause |
In an exhaust pipe, fine powder of SiOxNyHz (amorphous hydrogenated silicon compound) accumulated as a by-product. It was blown to an evil elimination apparatus due to a valve operation error, reacted with water and generated hydrogen. The hydrogen exploded on contact with an ignition source in the heater of the apparatus, and generated a blast, which dispersed the fine powder to cause a dust explosion. |
| Countermeasures |
Hazards of by-products are investigated. Safety of facilities is improved. A standard operating procedure is made and operations are conducted according to the standard, especially in handling flammables and/or combustible materials. Safety and health education for workers are executed. |
| Knowledge Comment |
In group work, all members must sufficiently understand the operation, and it is important to have enough communication. |
| Background |
Human error in a valve operation caused the accident. However, the preventive measure to eliminate the error should be established by the facilities managers considering this hazard. |
| Reason for Adding to DB |
Example of explosion of a semiconductor manufacturing plant, whose number is expected to increase in the future |
| Scenario |
| Primary Scenario
|
Poor Value Perception, Poor Safety Awareness, Inadequte Safety Measure, Ignorance of Procedure, Insufficient Communication, Insufficient Confirmation, Planning and Design, Poor Planning, Poor Planning of Repair, Incorrect Reaction, Poor Communication, Bad Event, Chemical Phenomenon, Abnormal Reaction, Secondary Damage, External Damage, Explosion, Bodily Harm, Death
|
|
| Sources |
Japan Industrial Safety and Health Assoc. Safety and health information center, Case of labor accident. No.100167. Explosion at by-product clean-up operation for exhaust air duct of the plant with a film on the silicon surface. The Japan Industrial Safety and Health Assoc. home page.
Explosion death accident examiner, Report on investigation of cause of explosion.
|
| Number of Deaths |
1 |
| Physical Damage |
Slight damage to a near flange opening. |
| Multimedia Files |
Fig3.Chemical formula
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Fig4.Chemical formula
|
| Field |
Chemicals and Plants
|
| Author |
ARAI, Mitsuru (Environmental Science Center, The University of Tokyo)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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